Tracy covered a great deal of information, both introducing the students to wetlands and wetland management in general, as well as covering the history and issues facing the Class of 1918 Marsh. He explained that every wetland is different and suggested a framework for determining the best management for a particular wetland: 1) How did the wetland function historically? In particular, where did the water come from and go? 2) What has changed since then? 3) In light of the changes, how can we restore conditions to get it to function more like it did historically?
Much of the talk pointed out the many changes that have occurred to the marsh since it was a sedge meadow in a lobe of Lake Mendota As expected many changes had to do with the flow of the water—University Bay Drive forms a levee cutting the marsh off from the lake, buildings and roads mean more runoff, more contaminants and flashier flows, and since Lake Mendota has been raised, water must now be pumped out of the marsh. Also the marsh was deepened as part of the restoration in the late 1960's, making it far wetter than the historical sedge meadow. Another significant change is the vegetation. The mowed recreation fields contribute to faster runoff and less infiltration. But the invasion of the hybrid cattails is a greater concern. These thrive with the high amount of nutrients and the stable water levels now present in the marsh, and can grow to be twenty times more dense than the native broad-leaf cattail. The current growth is far too dense for good habitat for many species. Reed-canary Grass is another invasive that can form dense mats choking out other plants.
In the discussion of opportunities for future management, Tracy suggested that perhaps one of the best things that could be realistically done in the marsh is vegetation control for the cattails. He described a cut-and-flood technique that has worked elsewhere. It turns out that cattails can actually be killed by cutting them low and then flooding them, which drowns the roots. It would be good, Tracy said, to experiment with some cattail control methods to see what might be the most practical approach in this situation.
In the end Tracy reminded us that, in spite of the many issues faced by the marsh, it still is providing services to the Preserve and the lake by managing runoff, filtering contaminants and providing habitat for wildlife and opportunities for recreation, and that it needs our protection and care to learn more about Wisconsin Wetlands Association and how you can help, please visit Wisconsinwetlands.org.
Summary by the Friends host Steve Sentoff. Photos Steve Sentoff and Gisela Kutzbach.